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  • 1
    Publication Date: 2011-07-01
    Description: The carbon ({delta}13Corg) and nitrogen ({delta}15N) isotopic compositions of bulk organic matter were analyzed in two high-resolution Permian-Triassic transitional sections containing microbialite in south China. The results from these shallow-marine sections show that an abrupt negative shift in {delta}15N, from [~]+3{per thousand} to [~]0{per thousand}, occurred immediately after the latest Permian mass extinction (LPE) in both sections, concurrent with a distinct negative shift in {delta}13Corg. The persistently low values of {delta}15N suggest that, following the LPE, microbial nitrogen fixation became the main source of biologically available nitrogen in the Nanpanjiang Basin and perhaps over a broader region of the eastern Paleotethys Ocean. Enhanced N fixation is probably indicative of the prevalence of stratified anoxic water masses characterized by intense denitrification and/or anaerobic ammonium oxidation at the time. Perturbation of the marine nitrogen cycle might have contributed to high temperatures following the main marine mass extinction through the release of the greenhouse gas N2O. The sharp declines in {delta}15N and {delta}13Corg may be ascribed to an abrupt change in shallow-water microbial communities, which differed in composition from contemporaneous deep-water communities.
    Print ISSN: 0091-7613
    Electronic ISSN: 1943-2682
    Topics: Geosciences
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  • 2
    Publication Date: 2015-02-04
    Description: Denitrification removes fixed nitrogen (N) from the biosphere, thereby restricting the availability of this key limiting nutrient for terrestrial plant productivity. This microbially driven process has been exceedingly difficult to measure, however, given the large background of nitrogen gas (N2) in the atmosphere and vexing scaling issues associated with heterogeneous...
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 3
    Publication Date: 2012-07-18
    Description: Graphene has attracted enormous attention for radio-frequency transistor applications because of its exceptional high carrier mobility, high carrier saturation velocity, and large critical current density. Herein we report a new approach for the scalable fabrication of high-performance graphene transistors with transferred gate stacks. Specifically, arrays of gate stacks are first patterned on a sacrificial substrate, and then transferred onto arbitrary substrates with graphene on top. A self-aligned process, enabled by the unique structure of the transferred gate stacks, is then used to position precisely the source and drain electrodes with minimized access resistance or parasitic capacitance. This process has therefore enabled scalable fabrication of self-aligned graphene transistors with unprecedented performance including a record-high cutoff frequency up to 427 GHz. Our study defines a unique pathway to large-scale fabrication of high-performance graphene transistors, and holds significant potential for future application of graphene-based devices in ultra–high-frequency circuits.
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 4
    Publication Date: 2011-08-31
    Description: Based on the crystal structure of the budding yeast Kluyveromyces lactis (Kl) Scm3–Cse4–H4 complex and the proteolysis results of the budding yeast Saccharomyces cerevisiae (Sc) Scm3–Cse4–H4 complex, Cho and Harrison (1) questioned our NMR structure of the Sc Scm3–Cse4–H4 complex (2), stating that “The construct deleted helix I of H4, however, and this deletion, together with omission of about 20 residues in the N-terminal part of the conserved region of Scm3, appears to have generated severe distortions in about half the structure, leading to incorrect conclusions about histone conformational differences and about a number of the Scm3-Cse4 contacts.”The statement by...
    Keywords: Letters
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 5
    Publication Date: 2014-04-10
    Description: Time-periodic perturbation can be used to modify the transport properties of the surface states of topological insulators, specifically their chiral tunneling property. Using the scattering matrix method, we study the tunneling transmission of the surface states of a topological insulator under the influence of a time-dependent potential and finite gate bias voltage. It is found that perfect transmission is obtained for electrons which are injected normally into the time-periodic potential region in the absence of any bias voltage. However, this signature of Klein tunneling is destroyed when a bias voltage is applied, with the transmission probability of normally incident electrons decreasing with increasing gate bias voltage. Likewise, the overall conductance of the system decreases significantly when a gate bias voltage is applied. The characteristic left-handed helicity of the transmitted spin polarization is also broken by the finite gate bias voltage. In addition, the time-dependent potential modifies the large-angle transmission profile, which exhibits an oscillatory or resonance-like behavior. Finally, time-dependent transport modes (with oscillating potential in the THz frequency) can result in enhanced overall conductance, irrespective of the presence or absence of the gate bias voltage. Scientific Reports 4 doi: 10.1038/srep04624
    Electronic ISSN: 2045-2322
    Topics: Natural Sciences in General
    Published by Springer Nature
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  • 6
    Publication Date: 2015-05-02
    Description: Werner syndrome (WS) is a premature aging disorder caused by WRN protein deficiency. Here, we report on the generation of a human WS model in human embryonic stem cells (ESCs). Differentiation of WRN-null ESCs to mesenchymal stem cells (MSCs) recapitulates features of premature cellular aging, a global loss of H3K9me3, and changes in heterochromatin architecture. We show that WRN associates with heterochromatin proteins SUV39H1 and HP1alpha and nuclear lamina-heterochromatin anchoring protein LAP2beta. Targeted knock-in of catalytically inactive SUV39H1 in wild-type MSCs recapitulates accelerated cellular senescence, resembling WRN-deficient MSCs. Moreover, decrease in WRN and heterochromatin marks are detected in MSCs from older individuals. Our observations uncover a role for WRN in maintaining heterochromatin stability and highlight heterochromatin disorganization as a potential determinant of human aging.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4494668/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4494668/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Zhang, Weiqi -- Li, Jingyi -- Suzuki, Keiichiro -- Qu, Jing -- Wang, Ping -- Zhou, Junzhi -- Liu, Xiaomeng -- Ren, Ruotong -- Xu, Xiuling -- Ocampo, Alejandro -- Yuan, Tingting -- Yang, Jiping -- Li, Ying -- Shi, Liang -- Guan, Dee -- Pan, Huize -- Duan, Shunlei -- Ding, Zhichao -- Li, Mo -- Yi, Fei -- Bai, Ruijun -- Wang, Yayu -- Chen, Chang -- Yang, Fuquan -- Li, Xiaoyu -- Wang, Zimei -- Aizawa, Emi -- Goebl, April -- Soligalla, Rupa Devi -- Reddy, Pradeep -- Esteban, Concepcion Rodriguez -- Tang, Fuchou -- Liu, Guang-Hui -- Belmonte, Juan Carlos Izpisua -- F32 AG047770/AG/NIA NIH HHS/ -- New York, N.Y. -- Science. 2015 Jun 5;348(6239):1160-3. doi: 10.1126/science.aaa1356. Epub 2015 Apr 30.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China. ; Biodynamic Optical Imaging Center, College of Life Sciences, Peking University, Beijing 100871, China. ; Gene Expression Laboratory, Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA. ; State Key Laboratory of Reproductive Biology, Institute of Zoology, Chinese Academy of Sciences, Beijing 100101, China. ; Diagnosis and Treatment Center for Oral Disease, the 306th Hospital of the PLA, Beijing, China. ; Department of Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA. ; College of Life Sciences, Peking University, Beijing 100871, China. ; The Center for Anti-aging and Regenerative Medicine, Shenzhen University, Shenzhen 518060, China. ; Gene Expression Laboratory, Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA. Universidad Catolica San Antonio de Murcia, Campus de los Jeronimos s/n, 30107 Guadalupe, Murcia, Spain. ; Biodynamic Optical Imaging Center, College of Life Sciences, Peking University, Beijing 100871, China. Ministry of Education Key Laboratory of Cell Proliferation and Differentiation, Beijing 100871, China. Center for Molecular and Translational Medicine (CMTM), Beijing 100101, China. Peking-Tsinghua Center for Life Sciences, Peking University, Beijing 100871, China. ghliu@ibp.ac.cn tangfuchou@pku.edu.cn belmonte@salk.edu. ; National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, Beijing 100101, China. The Center for Anti-aging and Regenerative Medicine, Shenzhen University, Shenzhen 518060, China. Center for Molecular and Translational Medicine (CMTM), Beijing 100101, China. Beijing Institute for Brain Disorders, Beijing 100069, China. ghliu@ibp.ac.cn tangfuchou@pku.edu.cn belmonte@salk.edu. ; Gene Expression Laboratory, Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA. ghliu@ibp.ac.cn tangfuchou@pku.edu.cn belmonte@salk.edu.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/25931448" target="_blank"〉PubMed〈/a〉
    Keywords: Aging/genetics/*metabolism ; Animals ; *Cell Aging ; Cell Differentiation ; Centromere/metabolism ; Chromosomal Proteins, Non-Histone/metabolism ; DNA-Binding Proteins/metabolism ; Epigenesis, Genetic ; Exodeoxyribonucleases/genetics/*metabolism ; Gene Knockout Techniques ; HEK293 Cells ; Heterochromatin/chemistry/*metabolism ; Humans ; Membrane Proteins/metabolism ; Mesenchymal Stromal Cells/*metabolism ; Methyltransferases/genetics/metabolism ; Mice ; Models, Biological ; RecQ Helicases/genetics/*metabolism ; Repressor Proteins/genetics/metabolism ; Werner Syndrome/genetics/*metabolism
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 7
    Publication Date: 2016-01-09
    Description: Splicing of precursor messenger RNA is accomplished by a dynamic megacomplex known as the spliceosome. Assembly of a functional spliceosome requires a preassembled U4/U6.U5 tri-snRNP complex, which comprises the U5 small nuclear ribonucleoprotein (snRNP), the U4 and U6 small nuclear RNA (snRNA) duplex, and a number of protein factors. Here we report the three-dimensional structure of a Saccharomyces cerevisiae U4/U6.U5 tri-snRNP at an overall resolution of 3.8 angstroms by single-particle electron cryomicroscopy. The local resolution for the core regions of the tri-snRNP reaches 3.0 to 3.5 angstroms, allowing construction of a refined atomic model. Our structure contains U5 snRNA, the extensively base-paired U4/U6 snRNA, and 30 proteins including Prp8 and Snu114, which amount to 8495 amino acids and 263 nucleotides with a combined molecular mass of ~1 megadalton. The catalytic nucleotide U80 from U6 snRNA exists in an inactive conformation, stabilized by its base-pairing interactions with U4 snRNA and protected by Prp3. Pre-messenger RNA is bound in the tri-snRNP through base-pairing interactions with U6 snRNA and loop I of U5 snRNA. This structure, together with that of the spliceosome, reveals the molecular choreography of the snRNAs in the activation process of the spliceosomal ribozyme.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Wan, Ruixue -- Yan, Chuangye -- Bai, Rui -- Wang, Lin -- Huang, Min -- Wong, Catherine C L -- Shi, Yigong -- New York, N.Y. -- Science. 2016 Jan 29;351(6272):466-75. doi: 10.1126/science.aad6466. Epub 2016 Jan 7.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Ministry of Education Key Laboratory of Protein Science, Tsinghua-Peking Joint Center for Life Sciences, Beijing Advanced Innovation Center for Structural Biology, School of Life Sciences, Tsinghua University, Beijing 100084, China. ; National Center for Protein Science Shanghai, Institute of Biochemistry and Cell Biology, Shanghai Institutes of Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26743623" target="_blank"〉PubMed〈/a〉
    Keywords: Catalysis ; Cryoelectron Microscopy ; Nucleic Acid Conformation ; Protein Conformation ; RNA Precursors/chemistry ; *RNA Splicing ; RNA, Messenger/chemistry ; RNA, Small Nuclear/*chemistry/ultrastructure ; Ribonucleoprotein, U4-U6 Small Nuclear/*chemistry/ultrastructure ; Ribonucleoprotein, U5 Small Nuclear/*chemistry/ultrastructure ; Saccharomyces cerevisiae/*metabolism ; Saccharomyces cerevisiae Proteins/*chemistry/ultrastructure ; Spliceosomes/*chemistry/ultrastructure
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 8
    Publication Date: 2016-12-01
    Description: Great effort has been applied to scientific research on the controllable synthesis of carbon nanotubes (CNTs) with high semiconducting selectivity or high areal density toward the macroscale applications of high-performance carbon-based electronics. However, the key issue of compatibility between these two requirements for CNTs remains a challenge, blocking the expected performance boost of CNT devices. We report an in situ acoustic-assisted assembly of high-density monochromatic CNT tangles (m-CNT-Ts), consisting of one self-entangled CNT with a length of up to 100 mm and consistent chirality. On the basis of a minimum consumed energy model with a Strouhal number of approximately 0.3, the scale could be controlled within the range of 1 x 10 4 to 3 x 10 4 μm 2 or even a larger range. Transistors fabricated with one m-CNT-T showed an on/off ratio of 10 3 to 10 6 with 4-mA on-state current, which is also the highest on-state current recorded so far for single CNT–based transistors. This acoustic-assisted assembly of chiral-consistent m-CNT-Ts will provide new opportunities for the fabrication of high-performance electronics based on perfect CNTs with high purity and high density.
    Electronic ISSN: 2375-2548
    Topics: Natural Sciences in General
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  • 9
  • 10
    Publication Date: 2018-02-21
    Description: Author(s): Yuan Li, H. B. Zhu, G. Q. Wang, Y. Z. Peng, J. R. Xu, Z. H. Qian, R. Bai, G. H. Zhou, C. Yesilyurt, Z. B. Siu, and M. B. A. Jalil We adopt the tight-binding mode-matching method to study the strain effect on silicene heterojunctions. It is found that valley- and spin-dependent separation of electrons cannot be achieved by the electric field only. When a strain and an electric field are simultaneously applied to the central sca... [Phys. Rev. B 97, 085427] Published Tue Feb 20, 2018
    Keywords: Surface physics, nanoscale physics, low-dimensional systems
    Print ISSN: 1098-0121
    Electronic ISSN: 1095-3795
    Topics: Physics
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